Well, when you're inverted for more than a few minutes, there are some problems that can develop. Inversion causes blood to pool in your upper body, which is not used to that pressure. This raises blood pressure in the upper body in an unusual way. What this means is that people with high blood pressure, glaucoma, and heart disease probably shouldn't do inversion play. Pregnant woman should also not do it. It can also put unusual strain on the spine and some bones that aren't intended to be load-bearing, so people with back problems, a history of fractures, osteoporosis, or similar conditions shouldn't do it. Finally, those who have had a stroke or aneurism shouldn't do it.

"We hurt the ones we love the most. It's a subtle form of compliment."

Yes, absolutely. I think most people will black out eventually. Assuming you're basically healthy and don't fit any of the categories I mentioned above, I think the take-away is that you could do it for a short period of time, but once you start feeling really uncomfortable, dizzy, headachy or whatever, you need to stop. Maybe try it for 5-10 minutes and see how you feel. If you tolerate it well, try a little longer.

"We hurt the ones we love the most. It's a subtle form of compliment."